In the prior art, an inverter apparatus for converting a single-phase signal to three-phase signals has comprised a three-phase full-wave converter circuit, as a phase shifting converter, which uses a semiconductor switching element for each of the three phases and applies three-phase A.C. signals each having a 120.degree. phase difference therebetween to the associated load coils in the three phases.
In general, with respect to the construction of a single-phase induction motor used for an electrically powered machine such as an air conditioner, a laundry machine and a refrigerator, which may be operated by a home-wired single-phase A.C. power source, a stator may be formed by a main winding and an auxiliary winding for a starting operation and a rotor may be of a cage type. As compared with a three-phase induction motor operated by an industrial power wiring, such single-phase induction motor is inferior in starting and other electric characteristics, requires a relatively large number of elements and becomes large in size. Also, it is impossible in such single-phase induction motor to effectively provide the winding throughout the periphery of the rotor, unlike a three-phase induction motor.
In order to self-start the single-phase induction motor, it is necessary to provide a shading coil, or a centrifugal contact and a phase advance capacitor. However, this complicates the mechanism of the motor.